The use of chlorate candles, also known as oxygen candles, for generating and supplying oxygen to closed spaces is well known. An example of a known oxygen candle furnace arrangement is illustrated in U.S. Pat. No. 3,385,672, which outlines various elements of an oxygen candle furnace, such as the hollow metal drum within which the candle burns. The hollow metal drum is typically covered with a metal lid which has a sealing gland thereon. The sealing gland helps to seal and maintain the integrity of the furnace. However, the patent does not describe or illustrate elements of the “sealing gland” fitting.
FIG. 1 is an exploded view of the typical prior art sealing gland 10. As shown, the sealing gland 10 includes a brass bulkhead fitting 25 having two threaded sections 20 and 40, separated by a hexagonal middle section 30 that may be gripped with a wrench during installation. The hexagonal middle section 30 also provides a bearing surface for fastening to the lid 15 of an oxygen candle furnace. The sealing gland 10 may be secured to the lid 15 by a washer and nut on the underside of the lid. As shown in FIG. 1, inside the sealing gland is a small brass washer 50, a coil of heat-resistant fiberglass yarn 55, and a brass ferrule 60. A brass compression nut 70 is threaded over the top portion of the bulkhead fitting. The coil of fiberglass yarn 55 rests on the washer 50, and is compacted by the nut 70 and ferrule 60. In operation, the fiberglass yarn 55 is located below the lid and within the furnace.
FIG. 1 also shows a borehole 80 through which an igniter nail extends. The fiberglass yarn 55 is intended to prevent combustion products from escaping the furnace via the borehole 80. Because the diameter of the borehole 80 is significantly wide, as compared to the diameter of the igniter nail, the fiberglass yarn 55 provides friction to secure the igniter nail in place and to restrict lateral movement thereof, before and during oxygen production. However, the fiberglass yarn 55 deteriorates due to high temperatures and exposure to combustion products. The location of the fiberglass yarn 55 within the furnace also contributes to its deterioration. The sealing gland 10 is not easily maintainable and difficult to support logistically. As the yarn deteriorates the passageway though the borehole 80 opens up. Thus, the bulkhead fitting does not function as a sealing gland, and does not securely hold the igniter nail. Smoke freely escapes the furnace through the opening. When this happens, operators are forced to bend the nail to hold it in place, which is undesirable as a bent nail is difficult to use for ignition, and often damages the oxygen candle. Alternatively, an external device, such as a binder clip may be used to secure the nail, which is also undesirable because typically, the igniter nail is not securely supported. Catastrophic failures of furnaces have been recorded when an improperly secured nail has fallen through a deteriorated sealing gland and has been consumed in the furnace, allowing a release of hot combustion products through the breach in the lid. Thus, it is desired to have a more secure means of holding the ignition nail and sealing an oxygen candle furnace arrangement.